Back up sensor



FIG. 1 is a perspective view of the back up sensor strip of the present invention;

FIG. 2 is a left side elevational view;

FIG. 3 is a right side elevational view;

FIG. 4 is a top plan view;

FIG. 5 is a front elevational view;

FIG. 6 is a bottom plan view; and,

FIG. 7 is a rear elevational view. 

The ornamental design for a back up sensor, as shown and described. 